This is classloading problem, due to different modules in enterprise application.
You have EffectiveArea class in ejb jar, and it content not availible in a web application. At rendering time, Seam ( as usual, seam.jar is placed at EAR level, and have access to all modules ) parse EL expression and store type of parameter into ActionExpression instance. At a RESTORE_VIEW phase, web content can't load this class for de-serialisation of a component attribute.
You can store row number as a parameter for a link, or use any simple class ( String, Integer etc ) for a expression parameter, like :
ok thanks for your reply.
i understand your point. but it is strange since it works except in the case there' s only one instance in the List. So the ClassLoading Exception is only thrown in this case.